1. Field of the Invention
The present invention relates to a method and equipment for flushing a water main and in particular to a pump and filter system and method of flushing a section of water main between hydrants filtering the sediment and particulates out of the water and recirculating it back into the water main without wasting the water.
2. Description of the Prior Art
Almost all water providers are required to have their mains large enough to provide a sufficient flow for fire protection. This means that the flow rate or velocities in the large mains during normal use are reduced significantly, allowing any particulates to settle to the bottom. After a length of time the particulates would build up and if there is any surges in the system the particulates are stirred up causing the water to appear dirty. To remedy this occurrence the entire system would have to be flushed annually from hydrants and blow-offs throughout the entire system. This method wastes millions of gallons of water each year, could possibly cause property damage, flooding the streets causing traffic problems and is usually performed at night to avoid the public eye, making the flushing procedure very costly.
In addition to the above problems new regulations require that the water be dechlorinated before it is allowed to drain into any storm drainage system and you will also be required to have a NPDES permit plus containment systems in place to protect against washing silt into the drains. Not to mention that you will need to shut down multiple valves to isolate the section of main that you want to flush.
From time to time, it is necessary to flush water systems which deliver potable tap water. This is especially the case with newly lined fresh water mains which have been repaired by lining interior surfaces of the mains with a resin material. Before water passing through a pipe which is used for drinking water purposes, it is necessary to thoroughly flush the mains with tap water. In order to maintain water quality, it is also necessary, from time to time, to flush local tap water delivery systems such as neighborhood and subdivision tap water systems.
Generally, discharges from potable water systems result from overflow, flushing, disinfection, hydrostatic testing, mechanical cleaning or dewatering of vessels or structures used to store or convey potable water. This frequently includes fire hydrant flushing in which high velocity streams are generated on the order of 2,000 gallons per minute for a period of 10-15 minutes. By periodically testing fire hydrants, it can be determined if sufficient water is available in the system for fire fighting purposes.
Potable tap water usually contains residual chlorine. The Federal Clean Water Act and state agency regulations regarding discharges of potable water, such as regulations promulgated by the Maryland Department of the Environment, require that total maximum daily amount of residual chlorine must be less than 0.1 mg/liter. At levels higher than 0.1 mg/liter, aquatic life is endangered and fish kills occur. Since potable tap water and water discharged from fire hydrants which originates with county and municipal water systems is necessarily initially chlorinated, heavy discharges of this water will adversely affect aquatic life unless the amount of residual chlorine is reduced to less than 0.1 mg/liter. In the past, this was either not done or, when done, was attempted by injecting sodium sulfite into the discharge stream. This is a difficult process to perform and monitor because it is necessary to dispense sodium sulfite in controlled amounts according to the volume of water being treated. If there is too much sodium sulfite, it can itself cause pollution problems by interfering with pH levels and if the amount is insufficient, there will be excessive residual chlorine. It has been found that the injection approach requires not only highly skilled personnel, but extensive training. Moreover, the end result is unpredictable.
While some attempts have been made at improving water main flushing systems, the real problems of water waste and water quality still remain to be addressed.
U.S. Pat. No. 6,227,463, issued May 8, 2001 to Porter, provides a water treating device for attachment directly to a hydrant outlet. Tap water supply systems are flushed by opening fire hydrants and running potable water through the fire hydrants for a period of time. Since potable water usually contains chlorine, it is necessary to remove the chlorine before the water enters rivers, streams and bays in order to protect aquatic life. This is accomplished by passing the water through a diffuser attached to the fire hydrant, which diffuser contains a mesh bag with a sodium sulfite tablet therein. This still wastes huge quantities of water and adds chemicals to water being discharged into the environment.
U.S. Pat. No. 6,170,514, issued Jan. 9, 2001 to Esmailzadeh, shows a city water flushing and sludge prevention control apparatus for use with a city water system having a plurality of street water mains interconnected by branch water mains and having hydrants connected to the branch water mains, a city water flushing and sludge prevention apparatus consisting of: a sludge-prevention control valve insertable into a branch water main between two street water mains and closer to one of the two street water mains; the sludge-prevention control valve in the closed position preventing water from flowing through the branch water main from the closer street water main during a flushing operation, whereby all water flows through the branch water main from the more distant street water main and thereby flushes the portion of the branch water main between the sludge-prevention control valve and the more distant street water main; and a control mechanism adapted to close and open the sludge-prevention control valve. Again, this system dumps a tremendous amount of water and does not treat the water.
U.S. Pat. No. 5,911,255, issued Jun. 15, 1999 to Bond, claims a pipe cleaning method and device utilizing a partial blockage object positioned in a water pipe for a method of cleaning deposits from the inside of a pipe, comprising flushing a liquid through the pipe, and locally increasing the liquid flow rate adjacent the pipe wall due to the presence of the object. This system requires opening a hydrant to release the water filled with particulates removed from the linings of the water mains.
U.S. Pat. No. 5,201,338, issued Apr. 13, 1993 to McKeague, describes a system and device for flushing water mains. A water distribution system includes flushing hydrants having buried valve assemblies and a removable top stock carried from valve assembly to valve assembly. A vertical marker replaces the top stock when the hydrant is not in use. The buried valve assembly includes a valve urged closed by water pressure and an actuator rod extending through a spider in the top of a vertical barrel. A lock nut on the upper end of the actuator holds the valve closed even if water pressure is lost. The upper end of the vertical barrel includes an internally threaded adapter. The top stock includes a casing which is externally threaded to mate with the adapter and a second rod which is threaded to mate with the actuator rod. The hydrant is assembled by removing the lock nut and screwing the parts together while an operating screw is swung free, then swinging the operating screw into engagement with the second rod. A preferred embodiment permits water samples to be taken from the hydrant. An alternative embodiment provides automatic draining systems to make the hydrant frost proof. Again, this system wastes large quantities of water and dumps water with chemicals into the environment.
What is needed is a system for periodically cleaning water mains which does not waste water or dump municipal water containing chemicals and pipe sediments into the environment.
An object of the present invention is to provide a system and method for periodically cleaning water mains without wasting water and without dumping the municipal water containing chemicals and pipe deposits and sediments into the environment.
A related object of the present invention is to utilize an enclosed system and method which pumps water out of the water main between hydrants at higher flow rates to release deposits, particulates and sediment from the water main and then pump the water through filters to clean out the deposits, particulates and sediment, pumping the cleaned water back into the water main, thereby not wasting any water and not pumping chlorinated water, deposits, particulates and sediments into the environment.
One more object of the present invention is to provide a mobile system mounted on a truck containing the hoses, pumps, and filters used for the method of cleaning the water main one section at a time between hydrants using the closed recirculating pumping, filtering, and flushing method.
In brief, the mobile re-circulating/filtering/flushing machine comprises a large bobtail truck, semi truck/trailer or just a trailer. Mounted to the truck/trailer vehicle is a large multi-media filter system with one to five filter vessels all depending on the flow requirements needed to serve a particular application. On the inlet side of the filter system is a check valve and a section of clear tube to visually inspect the influent or incoming water. On the outlet side of the filter system is a spring-loaded flapper valve to keep the system from draining after disconnecting. A recirculating pump is installed to move the water in the circuit. Both inlet and outlet is connected to the hydrant or blow-off with a flexible hose that is rolled up after use. The system further comprises a metering system for rate of flow and a chemical injector for the addition of chlorine etc. to the water system.
The method of using the portable re-circulating/filtering/flushing system comprises circulating the water of a desired portion of main (at a flow rate of approximately 5 feet per second) out of a hydrant or blow-off, through the filter system then back into the water main through another hydrant or blow-off. This procedure would clean the sediment out of the water system while eliminating the need to waste large volumes of water, dechlorinate, deal with NPDES requirements/permits, flooding, private property damage and traffic problems.
Other applications for this machine and method are tank draining, tank cleaning and other uses where wasting water could cause many problems.
An advantage of the present invention is that it preserves water.
Another advantage of the present invention is that it prevents the dumping of water containing chlorine and other chemicals, deposits, sediments, and particulates from the water main into the environment.
An additional advantage of the present invention is that it provides a means for meeting environmental requirements for periodic flushing of a water supply system.